SBS 2011 Exchange Activesyc Failure

I have a new installation of Microsoft Small Business Server 2011. I am testing the functionality of Exchange Activesync using microsoft remote connectivity analyzer, and am getting a failure when using user credentials:
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Attempting to send an Autodiscover POST request to potential Autodiscover URLs.
Autodiscover settings weren't obtained when the Autodiscover POST request was sent.
Test Steps
ExRCA is attempting to retrieve an XML Autodiscover response from URL https://********.xml for user ***@*************co.uk.
ExRCA failed to obtain an Autodiscover XML response.
Additional Details
None of the expected XML elements were found in the XML response.

My *’s !

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I am getting success when I use my own admin credentials though, so this must be a permissions thing somewhere. I did a fair bit of googling yesterday and I’m ruling out certificate, DNS, or path problems (!)
My understanding is that the .xml document is produced on a per user basis ‘on the fly’ whenever a request is generated, so maybe a write permission for Authenticated Users?
Any ideas?

I have an commercial SSL cert and the Activesync test work with the admin credentials. It is the Domain Users that have the problem.
I have an SRV record in DNS is the Microsoft Remote Connectin tool finding the server correctly.
I have checked the authenitcation on the Autodiscover site and they conform to the reccomendations. Interestingly if I click on 'view virtual directories' none are listed. Howerver, since I can successfully test the admin account this seems unlikely to be a cause of the problem.
I have checked as per alanharditsy and the allow inheritable permission is already ticked.

Now updated to Exchange SP2 but no differnet.
Every test in test-outlookwebservices for a regular user passed bar one, which was:
Error The certificate for the URL https://********.********.local/Autodiscover/Autodiscover.xml is incorrect. For SSL to work, the certificate needs to have a subject of *************.***********.local, but the subject that was found is remote.**************.co.uk. Consider correcting service discovery, or installing a correct SSL certificate.
I think the error is probably spurious (Maybe?) as it's not failing with external SSL.
The external SSL is fully validated in the earlier parts of the MRCA when I test both admin and user externally.
I have only a BT Business Hub which I believe to be correctly configured - again, the admin users have no problem with the tests.
Cheers.

I hang my head in shame. A mismatch between the email aliases, address names and login names...
Six hours and a lot of hair tearing, and I only just noticed.
Sorted. Sorry for the bother. And thanks to all.

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